The present invention relates to a semiconductor device manufacturing unit which is used to form plasma CVD films on semiconductor wafers.
In manufacturing semiconductor devices such as integrated circuits, vacuum evaporation, sputtering, plasma CVD (chemical vapor deposition), or electrolytic oxidation is usually employed for formation of films. Among these methods, the plasma CVD method is of particular interest because with it films can be achieved at low temperatures and the quality of the films thus deposited is most suitable for dry processes.
FIG. 1 shows a conventional parallel flat plate type semiconductor device manufacturing unit which implements the plasma CVD method. In FIG. 1, reference numeral 1 designates a chamber, 2 an RF (high frequency) electrode provided in the chamber 1, and 3 a susceptor. The electrode 2 generates a plasma gas a by which CVD films are formed on semiconductor wafers 4 on the susceptor 3.
The conventional unit is disadvantageous in the following points. As the flow of plasma gas a is not uniform, the formed CVD films are not uniform. In addition the number of semiconductor wafers processable in one batch is small. As the density of the plasma gas a is low, the speed of deposition of the CVD film is low and accordingly the time required for processing each batch of semiconductor wafers is long. Furthermore, it is difficult to control the temperature in the chamber 1 and hence the quality of the CVD films is unstable. As the temperature distribution is not uniform, flakes are liable to be formed on the electrode. Also, it requires much time to clean the electrode of the flakes. Moreover, as the flakes fall on the main surfaces of the wafers, it is difficult to obtain stable films which are of excellent quality.